Reversible memory loss in a mouse model of Alzheimer's disease

Article (PDF Available)inThe Journal of Neuroscience : The Official Journal of the Society for Neuroscience 22(15):6331-5 · September 2002with121 Reads
Source: PubMed
Abstract
Alzheimer's disease (AD) is a neurodegenerative condition, believed to be irreversible, characterized by inexorable deterioration of memory and intellect, with neuronal loss accompanying amyloid plaques and neurofibrillary tangles. In an amyloid precursor protein transgenic mouse model, Tg2576, little or no neuronal loss accompanies age-related memory impairment or the accumulation of Abeta, a 40-42 aa polypeptide found in plaques. Recently, we have shown inverse correlations between brain Abeta and memory in Tg2576 mice stratified by age (Westerman et al., 2002). Broadening the age range examined obscured this relationship, leading us to propose that small, soluble assemblies of Abeta disrupt cognitive function in these mice. Here we show that memory loss can be fully reversed in Tg2576 mice using intraperitoneally administered BAM-10, a monoclonal antibody recognizing the N terminus of Abeta. The beneficial effect of BAM-10 was not associated with a significant Abeta reduction, but instead eliminated the inverse relationship between brain Abeta and memory. We postulate that BAM-10 acts by neutralizing Abeta assemblies in the brain that impair cognitive function. Our results indicate that a substantial portion of memory loss in Tg2576 mice is not permanent. If these Abeta assemblies contribute significantly to memory loss in AD, then successfully targeting them might improve memory in some AD patients.
Brief Communication
Reversible Memory Loss in a Mouse Transgenic Model of
Alzheimer’s Disease
Linda A. Kotilinek,
1
Brian Bacskai,
2
Marcus Westerman,
1
Takeshi Kawarabayashi,
3
Linda Younkin,
3
Bradley T. Hyman,
2
Steven Younkin,
3
and Karen H. Ashe
1
1
Departments of Neurology and Neuroscience, University of Minnesota, Minneapolis 55455,
2
Department of Neurology,
Massachusetts General Hospital East, Charlestown, Massachusetts 02129, and
3
Department of Neuroscience, Mayo
Clinic, Jacksonville, Florida 32224
Alzheimer’s disease (AD) is a neurodegenerative condition, be-
lieved to be irreversible, characterized by inexorable deteriora-
tion of memory and intellect, with neuronal loss accompanying
amyloid plaques and neurofibrillary tangles. In an amyloid pre-
cursor protein transgenic mouse model, Tg2576, little or no
neuronal loss accompanies age-related memory impairment or
the accumulation of A
, a 40–42 aa polypeptide found in
plaques. Recently, we have shown inverse correlations be-
tween brain A
and memory in Tg2576 mice stratified by age
(Westerman et al., 2002). Broadening the age range examined
obscured this relationship, leading us to propose that small,
soluble assemblies of A
disrupt cognitive function in these
mice. Here we show that memory loss can be fully reversed in
Tg2576 mice using intraperitoneally administered BAM-10, a
monoclonal antibody recognizing the N terminus of A
. The
beneficial effect of BAM-10 was not associated with a signifi-
cant A
reduction, but instead eliminated the inverse relation-
ship between brain A
and memory. We postulate that BAM-10
acts by neutralizing A
assemblies in the brain that impair
cognitive function. Our results indicate that a substantial por-
tion of memory loss in Tg2576 mice is not permanent. If these
A
assemblies contribute significantly to memory loss in AD,
then successfully targeting them might improve memory in
some AD patients.
Key words: Alzheimer’s disease; transgenic; behavior; A
;
monoclonal antibodies; memory
The Tg2576 transgenic mouse model of Alzheimer’s disease
(AD), which overexpresses a mutant form of amyloid precursor
protein (APP), APP
K670/671L
, linked to early onset familial AD,
develops amyloid plaques and progressive cognitive deficits
(Hsiao et al., 1996). In these mice, A
begins to rise rapidly at 6
months, coincident with the appearance of detergent-insoluble
A
(Kawarabayashi et al., 2001), and memory ability declines
progressively thereafter (Westerman et al., 2002). Punctate, cored
plaques are present in 7- to 8-month-old mice; mature, diffuse
plaques appear at 12 months of age (Kawarabayashi et al.,
2001). Descriptive characterizations of the relationship between
memory and A
in Tg2576 mice (Westerman et al., 2002), along
with active A
immunization studies in Tg2576 and other APP
transgenic mice (Janus et al., 2000; Morgan et al., 2000), have
demonstrated that A
is necessary and sufficient to disrupt mem-
ory and have implicated a soluble A
assembly rather than the
accumulation of A
or amyloid plaques per se.
There have been no studies addressing whether the deleterious
effects of A
on cognitive function are permanent. Tg2576 mice
at 16 months of age with mature plaque deposition show no
neuronal or synaptic loss (Irizarry et al., 1997), leading us to
surmise that cognitive impairment in these mice might be attrib-
utable to neuronal dysfunction rather than neuronal degenera-
tion. Based on previous studies of the relationship between A
and memory in Tg2576 mice (Westerman et al., 2002), we hy-
pothesized that if cognitive deficits related to toxic A
assemblies
occur primarily in the absence of structural damage, then passive
administration of antibodies to A
might rapidly reverse learning
and memory deficits by neutralizing one or more critical A
species, thereby restoring normal cognitive function. To focus our
evaluation on alterations in cognitive function that occur before
plaque deposition, we tested Tg2576 mice at 9 –11 months after
the appearance of detergent-insoluble A
, but preceding the
accumulation of abundant mature amyloid plaques (Kawaraba-
yashi et al., 2001). At this age, punctate deposits are present but
are rare and difficult to quantify meaningfully. Because passive
immunization affects molecular targets more rapidly and selec-
tively than active immunization, we chose passive immunization
as a tool to clarify the molecular mechanism by which memory
loss occurs in Tg2576 mice.
MATERIALS AND METHODS
Mice and behavioral testing. Forty-three female Tg2576 mice, positive for
the HuAPP695.K670N/M671L transgene in a hybrid C57BL/6/SJL back-
ground (Hsiao et al., 1996), were longitudinally tested twice at 9 –11
months of age; a total of 17 Tg2576-positive mice (10 female, 7 male)
were longitudinally tested at 2 and 8 months of age, and 10 littermates
negative for the transgene (7 female, 3 male) were tested at 3 months of
Received April 1, 2002; revised May 10, 2002; accepted May 20, 2002.
This work was supported by National Institutes of Health Grants AG15453
(K.H.A., B.T.H., S.Y.), NS33249 (K .H.A.), MH65465 (K.H.A.), and AG08687
(B.T.H.); by a Pioneer Award from the Alzheimer’s Association (B.T.H.); and by
The Walter Family Foundation (B.T.H.). We gratef ully acknowledge Stefanie
Schrump, Deirdre Cooper-Blacketer, Jennifer Perry, Aaron Guimaraes, Jennifer
Lang, Jennifer Paulson, and Nardina Nash for their expertise and dedication testing
mice in the water maze. We thank Megan McLellan and Steve Kajdasz for technical
assistance with immunohistological procedures and Eugene Gnida for technical help
performing ELISAs.
Correspondence should be addressed to Karen H. Ashe, Department of Neurol-
ogy, Mayo Mail Code 295, 420 Delaware Street Southeast, Minneapolis, MN 55455.
E-mail: hsiao005@umn.edu.
T. Kawarabayashi’s present address: Department of Neurology, Okayama Uni-
versity Graduate School of Medicine, Okayama, 700-8558 Japan.
Copyright © 2002 Society for Neuroscience 0270-6474/02/226331-05$15.00/0
The Journal of Neuroscience, August 1, 2002, 22(15):6331–6335
age, in the reference memory version of the Morris water maze (Morris,
1984), as described previously (Westerman et al., 2002).
In the longitudinal experiment involving 9- to 11-month-old mice, a
baseline assessment of the cohort was obtained immediately before
immunization, rst in the visible-platform version of the water maze (3
d, eight trials per day) followed by hidden-platform testing (9 d, four
trials per day). The spatial memory for the platform position was evalu-
ated in 1 min probe trials administered at the beginning of days 4, 7, and
10 of hidden platform testing. Mice were allocated to the two treatment
groups that were counterbalanced on the basis of the mean of the three
baseline probe scores. All cues were changed, and the platform position
was shifted to the opposite quadrant during subsequent retesting of
immunized mice performed 1112 d after the termination of the baseline
water maze test. Only a hidden-platform version of the water maze test
was performed. The order of testing mice from different experimental
groups was random, and the experimenters were unaware of the treat-
ment group. Eight mice that were unable to learn the visible-platform
test or be led out of the pool with an escape scoop were removed from the
experiment, a proportion consistent with previous studies (Westerman et
al., 2002). One mouse died during baseline testing, before immunization,
and another mouse died 12 hr after the nal BAM-10 injection, reduc-
ing the nal control (IgG) and treatment (BAM-10) group sizes to 17 and
16, respectively. The latter mouse showed no signs of illness at the time
of injection, making it likely that the acute death was related to a
traumatic injection rather than to encephalitis.
Seventeen naive Tg2576 mice, along with 10 transgene-negative litter-
mates, were also tested at 2 and 3 months of age, respectively, using the
same protocol, except that these mice were prehandled before testing.
Prehandling consisted of performing preparative maneuvers resembling
procedures used during testing 8 10 times during the 23 weeks before
actual testing. Previous cross-sectional studies of spatial reference mem-
ory during the lifetime of Tg2576 mice in the C57BL/6/SJL background
have shown no differences between Tg2576 mice at 6 months of age and
nontransgenic littermates at 20 months of age (Westerman et al., 2002).
For this reason, we chose to compare Tg2576 mice at 911 months of age
with younger Tg2576 mice and nontransgenic littermates. At 8 months of
age, the 17 Tg2576 mice were allocated into two treatment groups coun-
terbalanced on the basis of mean probe scores at 2 months of age and
gender, treated with BAM-10 or nonspecic IgG, retested in the water
maze beginning at 8.3 months of age, and killed at 8.7 months of age.
Antibody selection and administration. BAM-10 (Sigma, St. Louis, MO)
is a mouse monoclonal antibody recognizing A
(112). BAM-10 was
chosen on the basis of its ability to bind A
in vivo. Because not all
antibodies bind to A
in its native conguration (B. Bacskai and B. T.
Hyman, personal communication), we used multiphoton microscopy, an
in vivo imaging method with 1
m resolution, to evaluate the effective-
ness of BAM-10 antibody in living Tg2576 mice. We puried, concen-
trated, and labeled BAM-10 with uorescein, and applied 510
lofa1
mg/ml solution directly to the cortical surface of 25-month-old Tg2576
mice. We then visualized the uorescence as described previously (Bac-
skai et al., 2001), readily imaging both senile plaques in the neuropil and
amyloid angiopathy in the living mouse brain. The in vivo immunouo-
rescent signal colocalized with thioavine S staining in cored plaques and
in amyloid angiopathy, as well as revealing nonthioavine S diffuse
deposits (data not shown). Diffuse but not cored deposits were reduced
by53%after3dinBAM-10-treated mice, an effect similar to that
obtained using another antibody recognizing the N terminus of A
, 10D6
(Bacskai et al., 2001) (data not shown).
Antibodies were administered intraperitoneally beginning 4 5 d after
the last day of baseline water maze pretesting in the longitudinal exper-
iment involving 9- to 11-month-old mice, and 7 d before water maze
testing in the experiment involving 8-month-old mice. One group of
Tg2576 mice received BAM-10 ascites lacking sodium azide preserva-
tive; the other group if mice received IgG (Sigma). Animals received 0.5
mg of antibody on days 1, 6, and 12 and received 0.25 mg of antibody on
day 4. Mice were killed on the last day of behavioral testing,5dafter the
last dose.
Serum antibody titers. BAM-10 serum titers were measured using an
adaptation of methods described previously (Schenk et al., 1999). Micro-
titer ELISA plates (Costar, Cambridge, MA) were coated with 1
gof
aggregated A
42 (American Peptide Company, Sunnyvale, CA) in PBS,
pH 8.5, and blocked with 1% BSA (Sigma) in PBS, pH 7.4. Plates were
washed with wash buffer (PBS, 0.05% Tween 20), and threefold serial
dilutions (1:50 to 1:1350) of mouse serum in PBS, 1% BSA, 0.05% Tween
20, and 0.02% sodium azide were incubated overnight at 4°C. Plates were
washed and incubated for 1 hr at room temperature in a 1:10,000 dilution
of sheep anti-mouse HRP conjugate (Jackson ImmunoResearch, West
Grove, PA) in PBS, 0.05% Tween, and 0.1% BSA. Plates were washed
and developed with 3,35,5 tetramethylbenzidine (1-Step Slow TMB;
Pierce, Rockford, IL). The reaction was stopped with an equal volume of
1
M H
2
SO
4
, and plates were read at 450 nm. Optical densities (ODs) of
equivalently diluted normal mouse serum were subtracted from test sera
to obtain the net OD. The antibody titer was dened as the dilution of
serum yielding a net OD that was 50% of the maximal signal for that
specimen.
A
measurements. A
was measured by ELISA using the 3160 capture
antibody described previously (Kawarabayashi et al., 2001).
RESULTS
BAM-10 restores spatial learning and memory
We measured spatial reference memory, using the Morris water
maze (Morris, 1984), immediately before and after treatment
with BAM-10 (Fig. 1). Training trials were delivered in blocks of
four trials per day, and probe trials were performed on the
mornings after the 12th, 24th, and 36th training trials. When
memory impairment in Tg2576 mice rst emerges at 911 months
of age, it can be overcome with extensive training, making Tg2576
mice appear to be comparable with nontransgenic littermates at
the end of training (Westerman et al., 2002). The slower rate of
learning of Tg2576 mice at this particular age is easily detectable
at the beginning of training, in the earlier probe scores (Wester-
man et al., 2002). The rst probe scores were therefore used to
assess treatment effects in this study.
Animals were assigned to BAM-10 or IgG groups after the
baseline maze, counterbalancing for probe scores. The percent-
age of time spent by mice in the target quadrant during the
baseline test in the BAM-10 and IgG groups was not signicantly
different. Mice received three injections of either 0.5 mg of
BAM-10 or nonspecic mouse IgG (days 1, 6, and 12 of the
experiment) with a booster of 0.25 mg on day 4. BAM-10 serum
titers, measured using an adaptation of methods described previ-
ously (Schenk et al., 1999), ranged from 1:100 to 1:1100 at 5 d
after the last dose. Performance in the water maze was reassessed
beginning on day 8. The two groups showed signicant differ-
ences in changes in performance between baseline and post-
treatment tests [p 0.03 by t test or by two-way (treatment-by-test
session) ANOVA with repeated measures], indicating a signi-
cant effect of treatment with BAM-10 (Fig. 2a).
Because not all mice deteriorate at the same rate, a minority of
Figure 1. Longitudinal experimental design using Tg2576 mice to deter-
mine whether memory loss, once present, can be restored. Spatial refer-
ence memory was measured, using the Morris water maze (Morris, 1984),
immediately before and after intraperitoneal administration of BAM-10,
a monoclonal antibody recognizing the N terminus of A
.
6332 J. Neurosci., August 1, 2002, 22(15):63316335 Kotilinek et al. Reversible Memory Loss in Tg2576 Mice
9- to 11-month-old mice showed superior performance (40%
of time in the target quadrant) comparable with that of the top
third of nontransgenic mice. We subsequently segregated the
mice on the basis of baseline scores into impaired (40% of
time in the target quadrant) and superior (40% of time in the
target quadrant) groups. To address the question of whether
BAM-10 reversed decits, we compared the magnitude of the
change between baseline and post-treatment scores in im-
paired mice only. There was a signicant treatment-by-test
session (baseline vs post-treatment) interaction in impaired
mice ( p 0.04 by two-way ANOVA with repeated measures)
(Fig. 2b). Post-treatment scores in impaired mice receiving
IgG showed essentially no change relative to baseline scores. In
contrast, impaired mice receiving BAM-10 demonstrated sig-
nicantly improved scores ( p 0.01 by paired t test) (Fig. 2b).
Remarkably, post-treatment memory ability in BAM-10-
treated mice was similar to that of nontransgenic mice tested at
3 months or transgenic mice tested at 2 months, before the
onset of memory loss (Fig. 2b), indicating that the memory
decits in 9- to 11-month-old Tg2576 mice were reversed and
memory was fully restored with BAM-10. These results are
supported by comparing the learning curves of retention for
BAM-10 and nonspecic IgG treatments in Tg2576 mice (Fig.
2c). BAM-10 restored the learning curve in 9- to 11-month-old
mice to resemble that of 2-month-old Tg2576 mice.
The restorative effects of BAM-10 were also evident when
acquisition of spatial reference information was examined in
impaired mice. We compared mean escape latencies on days 35,
because differences in the performance of Tg2576 mice at this age
were most pronounced during this phase of training, consistent
with the maximal sensitivity of the rst probe trial on day 4.
There was a signicant treatment-by-training session (baseline vs
post-treatment) interaction for mean escape latencies ( p 0.03
by two-way ANOVA with repeated measures). Mean escape
latencies measured before and after IgG administration showed
no signicant differences [mean difference, 2.5 sec; 95% con-
dence interval (CI), 2.8 to 7.8 sec; p 0.32 by paired t test] (Fig.
2d). In contrast, mean escape latencies after BAM-10 treatment
improved signicantly (mean difference, 6.3 sec; 95% CI, 0.3
to 12.2 sec; p 0.04 by paired t test) (Fig. 2d). We also observed
longer escape latencies on day 1 of the post-treatment test in both
groups of mice, suggesting a retest effect in which mice exhibited
retention of spatial information from the baseline water maze
test. The retest effect rapidly extinguished with retraining in the
BAM-10-treated mice but not in the IgG-treated mice. The
benecial effects of BAM-10 were apparent within 11 d of the rst
antibody dose, the smallest time interval we could measure in this
study, given the 8 d elapsing between the rst dose and the
commencement of retesting in the water maze and the 3 d
training interval until the rst probe trial.
No significant changes were observed in A
levels
After behavioral testing, the brains of 19 IgG-treated mice and 18
BAM-10-treated mice were sequentially extracted rst in Tris-
buffered saline (TBS), then in 2% SDS, and nally in 70% formic
acid (Kawarabayashi et al., 2001). A
40 and A
42 were then
analyzed in each fraction by sandwich ELISA. This analysis
showed that the improved performance in mice treated with
BAM-10 was not associated with any signicant reduction in total
A
or in A
40 or A
42 in any of the fractions analyzed (Fig. 3a).
Although BAM-10 was selected on the basis of its ability to bind
to and result in the disaggregation of diffuse A
deposits in
Tg2576 mice when very high concentrations were applied directly
to the brain, it is noteworthy that a similar effect on lowering A
in the brain was not apparent in mice receiving BAM-10
intraperitoneally.
Figure 2. Spatial reference learning and memory in 9-
to 11-month-old Tg2576 mice before and after treatment
with BAM-10 antibody. The change in retention of spa-
tial memory occurring as a result of receiving BAM-10
or IgG antibodies intraperitoneally was measured by
subtracting baseline scores from post-treatment scores to
obtain the change in percentage of time spent in the
target quadrant (Change in %-time). a, Mice 9 11
months of age receiving BAM-10 antibody showed sig-
nicantly greater improvement than mice receiving non-
specic IgG (*p 0.03 by t test; IgG, n 17; BAM-10,
n 16). b, In mice that were impaired at baseline
(40% of the time spent in the target quadrant), those
receiving BAM-10 antibody also showed signicantly
greater improvement than those receiving nonspecic
IgG (*p 0.04 by two-way ANOVA with repeated
measures; IgG, n 13; BAM-10, n 14). Post-
treatment performance of impaired mice receiving
BAM-10 antibody was signicantly higher than baseline
performance (*p 0.01 by paired t test) and was similar
to that of 2-month-old Tg2576 mice (n 17) and
3-month-old nontransgenic littermates (n 10). c,
BAM-10, but not nonspecic IgG, restored the retention
learning curve of 9- to 11-month-old Tg2576 mice to
resemble that of 2-month-old (Young) Tg2576 mice. d,
Acquisition of spatial reference memory improved in
impaired mice receiving BAM-10 antibody, with signif-
icantly reduced mean escape latencies on days 35(*p
0.04 by paired t test), but not in mice receiving nonspe-
cic IgG. There was a signicant treatment-by-training
session (baseline vs post-treatment) interaction ( p
0.03 by two-way ANOVA with repeated measures).
Kotilinek et al. Reversible Memory Loss in Tg2576 Mice J. Neurosci., August 1, 2002, 22(15):63316335 6333
BAM-10 eliminates the inverse relationship between
A
and memory
We have demonstrated previously that there was no obvious
relationship between A
and memory in Tg2576 mice unless the
mice were stratied by age, whereupon signicant inverse corre-
lations emerged (Westerman et al., 2002). Because A
rises very
rapidly between 8 and 12 months of age (Kawarabayashi et al.,
2001), tight stratication by age (in days) is necessary to obtain
signicant correlations between A
and memory during this time.
To assess the effect of BAM-10 on the relationship between A
and memory in Tg2576 mice, we measured brain A
and post-
treatment spatial reference memory in a second set of mice all
exactly 8.7 months of age (all born within 1 d), treated with either
BAM-10 or nonspecic IgG according to the same schedule as
mice in the previously described longitudinal experiment using 9-
to 11-month-old mice. As in the previous experiment, treatment
with BAM-10 signicantly improved memory but had no signi-
cant effect on total A
or on A
40 or A
42 in any of the three
fractions (data not shown). Analysis of the rst probe scores
showed a signicant negative correlation (r ⫽⫺0.88; p 0.004 by
regression ANOVA) between total A
and memory in eight mice
treated with nonspecic IgG (Fig. 3b). A similar negative corre-
lation was observed in these mice for both A
40 and A
42 in
each of the three fractions analyzed, with r values ranging from
0.70 to 0.87 and p values ranging from 0.005 to 0.05. Because
the improved spatial learning and memory in mice treated with
BAM-10 was not associated with a signicant reduction in A
, the
negative correlation between A
and probe scores was eliminated
by BAM-10 treatment. As shown in Figure 3c, there was no
signicant correlation between A
and probe scores in nine mice
treated with BAM-10 (r 0.11; p 0.78 by regression ANOVA).
Although serum BAM-10 titers showed a 10-fold range in
levels, there was no correlation between peripheral BAM-10
titers and probe scores (r
2
0.0002), indicating that the effect of
BAM-10 on memory did not depend on blood levels of the
antibody. These results suggest that BAM-10 enters the CNS and
rapidly neutralizes the deleterious effects of small A
assemblies
that interfere with cognitive function, thus restoring normal
memory in Tg2576 mice.
DISCUSSION
Active immunization with A
was rst shown to prevent amyloid
deposition (Schenk et al., 1999) and was subsequently shown to
prevent cognitive decline (Janus et al., 2000; Morgan et al., 2000)
in two APP transgenic models of AD. Passive administration of
A
antibodies intraperitoneally (Bard et al., 2000) as well as
direct application of A
antibodies to the brain (Bacskai et al.,
2001) resulted in a reduction of amyloid burden and A
levels and
a rapid dispersal of deposits. None of these studies addressed the
question of whether cognitive decits, once present, could be
restored to normal. Our results show that A
antibodies can
indeed reverse behavioral decits in a relatively short period of
time. Although the IgG-treated mice performed nearly as well as
BAM-10-treated mice after extensive training (data not shown),
this does not diminish the observation that learning and memory
occurred signicantly more slowly in the IgG-treated group.
We postulate that BAM-10, like other A
antibodies (Bard et
al., 2000), enters the CNS and acts by neutralizing soluble A
assemblies disrupting cognitive function. These results support
the model we developed to explain the relationship between A
Figure 3. A
levels in Tg2576 mice treated with BAM-10 or nonspecic
IgG antibody. Total A
is the sum of A
40 and A
42 in TBS, 2% SDS,
and formic acid (FA) soluble fractions measured as described previously
(Kawarabayashi et al., 2001). a, Treatment of mice with BAM-10 was not
associated with a signicant reduction in total A
or in A
40 or A
42 in
any of the fractions analyzed ( p values ranged from 0.2 to 0.9). Measure-
ments represent means SDs. Brain A
levels were correlated with
memory in 8.7-month-old Tg2576 mice treated with BAM-10 or nonspe-
cic IgG antibody. b, There was a signicant inverse correlation between
total A
and probe scores in control mice treated with nonspecic IgG. c,
Treatment with BAM-10 eliminated the correlation between total A
and
probe scores.
Figure 4. BAM-10 neutralizes the cognitively disruptive activity of small
A
assemblies in the brain. Top, Memory loss in Tg2576 mice appears to
be caused by small A
assemblies (stars) (Westerman et al., 2002) formed
during the conversion of A
monomers (circles) to amyloid deposits
(starbursts). Aging refers to the event or series of events occurring as
animals age leading to the initial aggregation of monomeric A
. Little is
known about what comprises these events. Bottom, BAM-10 penetrates
into the brain, where it may bind to these small A
assemblies, neutralize
their deleterious effects on cognitive function, and rapidly restore mem-
ory in Tg2576 mice. With prolonged treatment, a reduction in amyloid
deposits may occur.
6334 J. Neurosci., August 1, 2002, 22(15):63316335 Kotilinek et al. Reversible Memory Loss in Tg2576 Mice
and memory in Tg2576 mice (Westerman et al., 2002) (Fig. 4).
Whether the same reversal effect would occur in older Tg2576
mice, where the presumably small amounts of BAM-10 entering
the brain would bind to abundant amyloid deposits and therefore
might be less available to neutralize soluble A
assemblies, is
unknown. The direct interaction of BAM-10 with A
in the brain
is in contrast to the mechanism of action proposed for m266
which, when chronically administered, lowers brain A
levels
(DeMattos et al., 2001). It has been suggested that m266 exerts its
action primarily from outside of the CNS, by creating a periph-
eral A
sink that draws A
out of the brain by mass action
(DeMattos et al., 2001). We cannot exclude the possibility that
BAM-10 exerts a similar indirect effect on brain A
in Tg2576
mice. Arguing against this mechanism, however, are the insignif-
icant changes in brain A
after BAM-10 administration that are
in contrast to the dramatic improvement in memory and the
absence of any correlation between serum antibody titers and
memory. Whether m266 and BAM-10 operate at distinct sites is
an important question to resolve, because whether A
antibodies
act within or outside of the CNS has important implications for
potential inammatory reactions in human A
immunization
studies.
The rapid and full restoration of memory suggests that most if
not all of the memory impairment in Tg2576 mice at this age
occurs by this mechanism, and implies that little if any structural
damage is associated with this type of A
-mediated brain dys-
function. The possibility that memory loss in humans might be
reversed depends on the extent to which the same molecular
mechanism that disrupts cognitive function in Tg2576 mice also
exists in AD (Klein et al., 2001). Tg2576 mice may represent a
model in which memory loss in certain early stages of AD can be
studied. If A
species that functionally impair normal cognition
contribute signicantly to Alzheimers dementia, especially in the
early stages, then successfully targeting these species might im-
prove or restore cognitive function.
Note added in proof. Rapid reversal of memory loss has also
been shown in PDAPP mice receiving passively administered
m266 A
antibodies (Dodart et al., 2002), which, together with
the ndings reported here, suggests a common mechanism for
memory loss in transgenic APP mice.
REFERENCES
Bacskai BJ, Kajdasz ST, Christie RH, Carter C, Games D, Seubert P,
Schenk D, Hyman BT (2001) Imaging of amyloid-
deposits in brains
of living mice permits direct observation of clearance of plaques with
immunotherapy. Nat Med 7:369 372.
Bard F, Cannon C, Barbour R, Burke RL, Games D, Grajeda H, Guido
T, Hu K, Huang J, Johnson-Wood K , Khan K, Kholodenko D, Lee M,
Lieberburg I, Motter R, Nguyen M, Soriano F, Vasquez N, Weiss K,
Welch B, et al (2000) Peripherally administered antibodies against
amyloid
-peptide enter the central nervous system and reduce pathol-
ogy in a mouse model of Alzheimer disease. Nat Med 6:916 919.
DeMattos RB, Bales KR, Cummins DJ, Dodart JC, Paul SM, Holtzman
DM (2001) Peripheral anti-A
antibody alters CNS and plasma A
clearance and decreases brain A
burden in a mouse model of Alzhei-
mers disease. Proc Natl Acad Sci USA 98:88508855.
Dodart JC, Bales KR, Gannon KS, Greene SJ, DeMattos RB, Mathis C,
DeLong CA, Wu S, Wu X, Holtzman DM, Paul SM (2002) Immuni-
zation reverses memory decits without reducing brain Abeta burden in
Alzehimers disease model, Nat Neurosci 5:452 457.
Hsiao K, Chapman P, Nilsen S, Eckman C, Harigaya Y, Younkin S, Yang
F, Cole G (1996) Correlative memory decits, A
elevation, and amy-
loid plaques in transgenic mice. Science 274:99 102.
Irizarry MC, McNamara M, Fedorchak K, Hsiao K, Hyman BT (1997)
APPSw transgenic mice develop age-related A
deposits and neuropil
abnormalities, but no neuronal loss in CA1. J Neuropathol Exp Neurol
56:965973.
Janus C, Pearson J, McLaurin J, Mathews PM, Jiang Y, Schmidt SD,
Chishti MA, Horne P, Heslin D, French J, Mount HT, Nixon RA,
Mercken M, Bergeron C, Fraser PE, St George-Hyslop P, Westaway D
(2000) A
peptide immunization reduces behavioural impairment and
plaques in a model of Alzheimers disease. Nature 408:979 982.
Kawarabayashi T, Younkin LH, Saido TC, Shoji M, Ashe KH, Younkin
SG (2001) Age-dependent changes in brain, C SF, and plasma amyloid
protein in the Tg2576 transgenic mouse model of Alzheimersdis-
ease. J Neurosci 21:372381.
Klein WL, Krafft GA, Finch CE (2001) Targeting small A
oligomers:
the solution to an Alzheimers disease conundrum? Trends Neurosci
24:219224.
Morgan D, Diamond DM, Gottschall PE, Ugen KE, Dickey C, Hardy J,
Duff K, Jantzen P, DiCarlo G, Wilcock D, Connor K, Hatcher J, Hope
C, Gordon M, Arendash GW (2000) A
peptide vaccination prevents
memory loss in an animal model of Alzheimers disease. Nature
408:982985.
Morris R (1984) Developments of a water-maze procedure for studying
spatial learning in the rat. J Neurosci Methods 11:47 60.
Schenk D, Barbour R, Dunn W, Gordon G, Grajeda H, Guido T, Hu K,
Huang J, Johnson-Wood K, Khan K, Kholodenko D, Lee M, Liao Z,
Lieberburg I, Motter R, Mutter L, Soriano F, Shopp G, Vasquez N,
Vandevert C, et al (1999) Immunization with amyloid-
attenuates
Alzheimer-disease-like pathology in the PDAPP mouse. Nature
400:173177.
Westerman M, Cooper-Blacketer D, Mariash A, Kotilinek L, Kawaraba-
yashi T, Younkin L H, C arlson G, Younkin SG, Ashe KH (2002) The
relationship between A
and memory in the Tg2576 mouse model of
Alzheimers disease. J Neurosci 22:1858 1867.
Kotilinek et al. Reversible Memory Loss in Tg2576 Mice J. Neurosci., August 1, 2002, 22(15):63316335 6335
    • "Since deglycosylation impairs the binding of the FcγRs to the antigen–antibody complex and complement activation, this strategy has been increasingly recognized as a targeted treatment of certain autoimmune conditions [151]. For example, immunotherapy that targets the amyloid-β (Aβ) protein has been investigated for Alzheimer's disease [152][153][154][155][156] . Despite being effective, systemic administration of anti-Aβ antibodies using unmodified IgG can provoke neuroinflammation via microglial activation and thus increases the risk of vascular amyloid and brain microhemorrhage [156][157][158]. "
    [Show abstract] [Hide abstract] ABSTRACT: Healthy human serum IgG contains multiple glycoforms which exhibit a range of binding properties to effector molecules such as cellular Fc receptors. Emerging knowledge of how the Fc glycans contribute to the antibody structure and effector functions has opened new avenues for the exploitation of defined antibody glycoforms in the treatment of diseases. Here, we review the structure and activity of antibody glycoforms and highlight developments in antibody glycoengineering by both the manipulation of the cellular glycosylation machinery and by chemoenzymatic synthesis. We discuss wide ranging applications of antibody glycoengineering in the treatment of cancer, autoimmunity and inflammation.
    Full-text · Article · Apr 2016
    • "Novel protocols and methods need to be established to provide reliable and valid detection of initial stages of p-preAD. In the light of the experience with Ab immunization (Balakrishnan et al., 2015; Bard et al., 2000; Clavaguera et al., 2009; Doody et al., 2014; Holmes et al., 2008; Iba et al., 2015; Kane et al., 2000; Kotilinek et al., 2002; Lannfelt et al., 2014; Meyer-Luehmann et al., 2006; Peeraer et al., 2015; Saido et al., 1995; Saido et al., 1996; Salloway et al., 2014; Schenk et al., 1999; Schilling et al., 2008; Stancu et al., 2015; Thal, Walter et al., 2015), I think that it will be essential to focus not only on preAD cases but also to take into account the stage of p-preAD pathology as well the proposed therapeutic mechanism to estimate whether a trial can be successful or not even when non-demented preAD cases are treated. In this respect, it is important to keep in mind that the currently available biomarkers for AD identify advanced p-preAD pathology when identifying non-demented individuals as preAD patients. "
    [Show abstract] [Hide abstract] ABSTRACT: The current gold standard for the diagnosis of Alzheimer’s disease (AD) is the pathological examination at autopsy. Clinical diagnostic procedures are quite well developed for symptomatic AD and permit a reliable and valid identification of AD patients. Today, there is strong interest to diagnose AD already in a preclinical stage to include protective treatment strategies into the treatment regimes for AD. This is important because current therapies for AD mainly focus on symptomatic improvement rather than on delaying disease progression. The current diagnostic criteria for preclinical AD (preAD) rely on biomarker profiles indicative for AD in non-demented individuals. At autopsy, pathological lesions considered to represent AD pathology permit the classification of non-demented cases exhibiting AD pathology as pathologically-defined preAD (p-preAD) cases. Recent studies investigating amyloid imaging as a biomarker and comparing it with the post-mortem findings on AD pathology revealed that preAD cases identified clinically by amyloid imaging already exhibited advanced stages of AD pathology whereas p-preAD cases with initial AD lesions failed clinical detection. In this article I will discuss these findings and its potential impact on clinical studies aimed at stopping or delaying the progression from preAD to symptomatic AD as well as on the interpretation of imaging or biomarker data in relation to the underlying disease progress with a focus on propagation and maturation of Aβ and τ pathology in-p-preAD.
    Article · Jan 2016
    • "Even the amount of fibrillar, Thioflavin S-positive plaques was reduced in anti-Aβ treated animals [6]. However, another group could not confirm Aβ reduction though an improvement of memory dysfunction was observed789. Active immunization in PDAPP mice demonstrated more effective rescue from cognitive impairment when treatment was started to prevent Aβ pathology compared to mice treated at a later point in life in a reversal trial [10]. "
    [Show abstract] [Hide abstract] ABSTRACT: The deposition of the amyloid β protein (Aβ) in the brain is a hallmark of Alzheimer's disease (AD). Removal of Aβ by Aβ-antibody treatment has been developed as a potential treatment strategy against AD. First clinical trials showed neither a stop nor a reduction of disease progression. Recently, we have shown that the formation of soluble and insoluble Aβ aggregates in the human brain follows a hierarchical sequence of three biochemical maturation stages (B-Aβ stages). To test the impact of the B-Aβ stage on Aβ immunotherapy, we treated transgenic mice expressing human amyloid precursor protein (APP) carrying the Swedish mutation (KM670/671NL; APP23) with the Aβ-antibody β1 or phosphate-buffered saline (PBS) beginning 1) at 3 months, before the onset of dendrite degeneration and plaque deposition, and 2) at 7 months, after the start of Aβ plaque deposition and dendrite degeneration. At 5 months of age, first Aβ aggregates in APP23 brain consisted of non-modified Aβ (representing B-Aβ stage 1) whereas mature Aβ-aggregates containing N-terminal truncated, pyroglutamate-modified AβN3pE and phosphorylated Aβ (representing B-Aβ stage 3) were found at 11 months of age in both β1- and PBS-treated animals. Protective effects on commissural neurons with highly ramified dendritic trees were observed only in 3-month-old β1-treated animals sacrificed at 5 months. When treatment started at 7 months of age, no differences in the numbers of healthy commissural neurons were observed between β1- and PBS-treated APP23 mice sacrificed with 11 months. Aβ antibody treatment was capable of protecting neurons from dendritic degeneration as long as Aβ aggregation was absent or represented B-Aβ stage 1 but had no protective or curative effect in later stages with mature Aβ aggregates (B-Aβ stage 3). These data indicate that the maturation stage of Aβ aggregates has impact on potential treatment effects in APP23 mice.
    Full-text · Article · Jul 2015
Show more

Recommended publications

Discover more